Rickettsia-host interface and multiple paths to invasion

项目总结 立克次体是革兰氏阴性专性胞内细菌，具有共生和 致病生命周期。立克次体感染的全球影响体现在感染的死灰复燃上。 在南美洲和中美洲感染立克次体(落基山斑点热的病原体)的人中， 或者欧洲、中东和非洲的康诺里杆菌(布通奈斯热)。引人注目的是，扁虱和跳蚤传播 立克次体疾病在美国也在上升，最近爆发的立克次体就是例证。 在亚利桑那州以及加利福尼亚州和德克萨斯州的伤寒杆菌(鼠斑疹伤寒的病原体)，进一步突出了 立克次体疾病的威胁。目前没有预防立克次体病的疫苗，我们的疫苗不足 对立克次体细胞内生活方式的理解阻碍了有效立克次体的发展 针对这些日益公认的细菌病原体的治疗。在过去的四年里，我们确定了 一种复杂的机制，致病立克次体利用分泌的效应物通过以下方式促进定植 操纵内质网结构或通过调节细胞内运输来颠覆宿主防御途径。 然而，致病立克次体物种利用这种效应器武器库颠覆 支持内皮细胞或巨噬细胞内生活方式的宿主天然防御途径(MΦ) 仍然没有明确的定义。为了解决这些知识差距，这一续订申请建议：i)破译如何 强毒立克次体利用它们的效应器来操纵自噬反应来定植宿主 细胞，以及ii)决定致病但不致病的立克次体的效应因子的机制(S) 抑制炎性小体激活，操纵M-Φ极化促进宿主扩散。我们的 总体目标是测试来自像Risk1这样的致病立克次体的效应器诱导 自噬负性调节炎性小体激活并使M-Φ极化从M1偏向M2偏向 为寄主殖民提供便利。为了检验我们的假设，在目标1中，我们将定义机制(S) 致病性立克次体颠覆自噬成熟，促进宿主定植。在目标2中，我们将 解读M-Φ颠覆炎症体反应和操纵的机制(S) 致病立克次体物种的极化。这些目标旨在揭示一种联系，通过这种联系，效应器 致病性立克次体操纵自噬来逆转依赖炎症体的促炎作用 细胞因子信号转导和M-Φ极化从杀微生物活性环境(M1-MΦ)向更有利的环境偏向 微生物环境(M2-MΦ)。这些研究将导致确定可以利用的联系 用于抗毒力策略。

PROJECT SUMMARY Species in the genus Rickettsia are Gram-negative obligate intracellular bacteria with both symbiotic and pathogenic lifecycles. The global impact of rickettsial infections is illustrated by the resurgence of infections of humans with R. rickettsia (etiologic agent of Rocky Mountain Spotted Fever) in South and Central America, or R. conorii (Boutonneuse fever) in Europe, the Middle East, and Africa. Strikingly, tick- and flea-borne rickettsial diseases are also on the rise in the United States, as exemplified by recent outbreaks of R. rickettsii in Arizona and R. typhi (etiologic agent of murine typhus) in California and Texas, further highlighting the threats of rickettsial diseases. There are currently no vaccines to prevent rickettsioses and our insufficient understanding of rickettsial intracellular lifestyle hinders the progression towards the development of effective therapeutics against these increasingly recognized bacterial pathogens. Over the past four years, we identified a complex mechanism by which pathogenic rickettsiae utilize secreted effectors to facilitate colonization by manipulating ER structures or by modulating intracellular trafficking to subvert host defense pathways. However, the precise mechanisms by which virulent Rickettsia species utilize this effector arsenal to subvert host innate defense pathways to support intracellular lifestyle in endothelial cells or macrophages (MΦ) remains ill-defined. To address these knowledge gaps, this renewal application proposes to: i) decipher how virulent Rickettsia species utilize their effector repertoire to manipulate autophagic responses to colonize host cells, and ii) determine the mechanism(s) by which effectors of virulent, but not avirulent, Rickettsia species suppress inflammasome activation and manipulate MΦ polarization to promote host dissemination. Our overall goal is to test the hypothesis that effectors from virulent species of Rickettsia, like Risk1, induce autophagy to negatively regulate inflammasome activation and skews MΦ polarization from a M1 to M2 bias to facilitate host colonization. To test our hypothesis, in Aim 1, we will define the mechanism(s) by which pathogenic Rickettsia subvert autophagosomal maturation to promote host colonization. In Aim 2, we will decipher the mechanism(s) underlying subversion of inflammasome responses and manipulation of MΦ polarization by pathogenic Rickettsia species. These Aims are intended to unveil a link by which effectors of pathogenic Rickettsia species manipulate autophagy to subvert inflammasome-dependent proinflammatory cytokine signaling and skew MΦ polarization from a microbicidal milieu (M1-MΦ) to a more favorable pro- microbial environment (M2-MΦ). These studies will lead to the identification of a link that could be exploited for anti-virulence strategy.